DIRECTIONS
Heat oven to 425°F. In medium cast iron skillet over medium heat, melt butter. Add carrots, celery, and onions. Cook 5 to 7 minutes or until softened. Add flour, thyme, salt and pepper. Cook 1 to 2 minutes. Add milk and broth. Simmer, whisking together 3 to 4 minutes or until combined and slightly thickened. Stir in peas, chopped chicken and gravy. Remove from heat.
On a lightly floured surface, roll out pastry sheet into a 16-inch square. Cut pastry into 2 to 3-inch squares.
Place dough squares, slightly overlapping on top of chicken mixture. Brush dough squares with beaten egg. Bake 25 to 30 minutes or until pastry is golden brown and filling is bubbly.